Vector length variance check for functional safety of angle sensors

ABSTRACT

A magnetic angle sensor system includes a first magnetic sensor configured to generate a first sensor signal, a second magnetic sensor configured to generate a second sensor signal, and at least one signal processor configured to: generate an angle signal including an angular value corresponding to an orientation of a magnetic field based on the first sensor signal and the second sensor signal; generate a vector length signal comprising a plurality of vector lengths corresponding to the first sensor signal and the second sensor signal; determine a vector length variance between at least two consecutively sampled vector lengths of the plurality of vector lengths; compare the determined vector length variance to a tolerance range defined by at least one of a minimum tolerance threshold and a maximum tolerance threshold; and generate a warning signal on a condition that the determined vector length variance is outside the tolerance range.

FIELD

The present disclosure relates generally to magnetic field anglesensors, and, more particularly, to performing functional safety checkson magnetic field angle sensors.

BACKGROUND

Today, vehicles feature numerous safety, body, and powertrainapplications that rely on magnetic position and angle sensors. Amagnetic angle sensor may be used to detect a rotational position ormovement of a shaft or other rotatable object. For example, in ElectricPower Steering (EPS), magnetic angle sensors can be used to measuresteering angle and steering torque for steering wheel sensing. Modernpowertrain systems can rely on magnetic angle sensors for camshaft,crankshaft, and transmission applications.

In addition, functional safety of electronic systems in automotivepassenger cars is an important topic in the light of increasingautomation and semiconductor content of modern cars. It is desirable tohave a reliable and safe functionality for the safety critical partsdeployed in the system.

One requirement, which may often exist in such safety-criticalapplications, is that malfunctions of a sensor device have to bedetectable by the system, for example by an entity receiving signalsfrom the sensor device. In other words, according to such a requirementit has to be possible to detect, if a sensor device delivers erroneousvalues, e.g., due to a fault of the sensor device.

Monitoring a vector length is known as an effective safety mechanism formagnetic field angle sensors. However, its diagnostic coverage heavilydepends on the sensor technology and the compensation of environmentaland device influences, such as temperature, stress, age, etc.

Thus, a device that is configured to verify the functionality of anangle sensor may be desirable. It may be further desirable to performthe verification while taking into account environmental and deviceinfluences.

SUMMARY

One or more embodiments are directed to a performing a vector lengthvariance check on angel sensors for enhancing functional safety of theangle sensor.

One or more embodiments provide magnetic angle sensor that includes afirst magnetic sensor configured to generate a first sensor signal inresponse to a first component of a magnetic field; a second magneticsensor configured to generate a second sensor signal in response to asecond component of the magnetic field; and at least one signalprocessor. The at least one signal processor is configured to: generatean angle signal including an angular value corresponding to anorientation of the magnetic field based on the first sensor signal andthe second sensor signal; generate a vector length signal comprising aplurality of vector lengths corresponding to the first sensor signal andthe second sensor signal based on the first sensor signal and the secondsensor signal, where each of the plurality of vector lengths is sampledat a different sample time of a plurality of consecutive sample times;determine a vector length variance between at least two consecutivelysampled vector lengths of the plurality of vector lengths; compare thedetermined vector length variance to a tolerance range defined by atleast one of a minimum tolerance threshold and a maximum tolerancethreshold; and generate a warning signal on a condition that thedetermined vector length variance is outside the tolerance range.

One or more further embodiments provide magnetic angle sensor thatincludes a first magnetic sensor configured to generate a first sensorsignal in response to a first component of a magnetic field; a secondmagnetic sensor configured to generate a second sensor signal inresponse to a second component of the magnetic field; and at least onesignal processor. The at least one signal processor is configured to:generate an angle signal including an angular value corresponding to anorientation of the magnetic field based on the first sensor signal andthe second sensor signal; generate a vector length signal comprising aplurality of vector lengths corresponding to the first sensor signal andthe second sensor signal based on the first sensor signal and the secondsensor signal, where each of the plurality of vector lengths is sampledat a different sample time of a plurality of consecutive sample times;extract at least one spectral component of the vector length signal, theat least one spectral component being indicative of a vector lengthvariance between at least two consecutively sampled vector lengths ofthe plurality of vector lengths; and generate a warning signal on acondition that the at least one extracted spectral component is outsidea tolerance range.

One or more further embodiments provide a method of performing a vectorlength variance check. The method includes generating a first sensorsignal in response to a first component of a magnetic field; generatinga second sensor signal in response to a second component of the magneticfield; generating an angle signal including an angular valuecorresponding to an orientation of the magnetic field based on the firstsensor signal and the second sensor signal; generating a vector lengthsignal comprising a plurality of vector lengths corresponding to thefirst sensor signal and the second sensor signal based on the firstsensor signal and the second sensor signal, where each of the pluralityof vector lengths is sampled at a different sample time of a pluralityof consecutive sample times; determining a vector length variancebetween at least two consecutively sampled vector lengths of theplurality of vector lengths; comparing the determined vector lengthvariance to a tolerance range defined by at least one of a minimumtolerance threshold and a maximum tolerance threshold; and generating awarning signal on a condition that the determined vector length varianceis outside the tolerance range.

One or more further embodiments provide a method of performing a vectorlength variance check. The method includes generating a first sensorsignal in response to a first component of a magnetic field; generatinga second sensor signal in response to a second component of the magneticfield; generating an angle signal including an angular valuecorresponding to an orientation of the magnetic field based on the firstsensor signal and the second sensor signal; generating a vector lengthsignal comprising a plurality of vector lengths corresponding to thefirst sensor signal and the second sensor signal based on the firstsensor signal and the second sensor signal, where each of the pluralityof vector lengths is sampled at a different sample time of a pluralityof consecutive sample times; extracting at least one frequency componentof the vector length signal, the at least one frequency component beingindicative of a vector length variance between at least twoconsecutively sampled vector lengths of the plurality of vector lengths;and generating a warning signal on a condition that the at least oneextracted frequency component is outside a tolerance range.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described herein making reference to the appendeddrawings.

FIG. 1 is a block diagram illustrating a magnetic angle sensor accordingto one or more embodiments;

FIG. 2A is a schematic block diagram of a magnetic angle sensor deviceaccording to one or more embodiments;

FIG. 2B is a graph illustrating a vector length tolerance regionaccording to one or more embodiments;

FIG. 3 is a schematic block diagram of another magnetic angle sensordevice according to one or more embodiments; and

FIG. 4 is a schematic block diagram of another magnetic angle sensordevice according to one or more embodiments.

DETAILED DESCRIPTION

In the following, details are set forth to provide a more thoroughexplanation of the exemplary embodiments. However, it will be apparentto those skilled in the art that embodiments may be practiced withoutthese specific details. In other instances, well-known structures anddevices are shown in block diagram form or in a schematic view ratherthan in detail in order to avoid obscuring the embodiments. In addition,features of the different embodiments described hereinafter may becombined with each other, unless specifically noted otherwise.

Further, equivalent or like elements or elements with equivalent or likefunctionality are denoted in the following description with equivalentor like reference numerals. As the same or functionally equivalentelements are given the same reference numbers in the figures, a repeateddescription for elements provided with the same reference numbers may beomitted. Hence, descriptions provided for elements having the same orlike reference numbers are mutually exchangeable.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

In embodiments described herein or shown in the drawings, any directelectrical connection or coupling, i.e., any connection or couplingwithout additional intervening elements, may also be implemented by anindirect connection or coupling, i.e., a connection or coupling with oneor more additional intervening elements, or vice versa, as long as thegeneral purpose of the connection or coupling, for example, to transmita certain kind of signal or to transmit a certain kind of information,is essentially maintained. Features from different embodiments may becombined to form further embodiments. For example, variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments unless noted to the contrary.

Embodiments relate to sensors and sensor systems, and to obtaininginformation about sensors and sensor systems. A sensor may refer to acomponent which converts a physical quantity to be measured to anelectric signal, for example, a current signal or a voltage signal. Thephysical quantity may for example comprise a magnetic field, an electricfield, a pressure, a force, a current or a voltage, but is not limitedthereto.

A magnetic field sensor, for example, includes one or more magneticfield sensing elements that measure one or more characteristics of amagnetic field (e.g., an amount of magnetic field flux density, a fieldstrength, a field angle, a field direction, a field orientation, etc.).The magnetic field may be produced by a magnet, a current-carryingconductor (e.g., a wire), the Earth, or other magnetic field source.Each magnetic field sensing element is configured to generate a sensorsignal (e.g., a voltage signal) in response to one or more magneticfields impinging on the sensing element. Thus, a sensor signal isindicative of the magnitude and/or the orientation of the magnetic fieldimpinging on the sensing element.

It will be appreciated that the terms “sensor” and “sensing element” maybe used interchangeably throughout this description, and the terms“sensor signal” and “measurement signal” may be used interchangeablythroughout this description.

Magnetic sensors provided in the described embodiments may include oneor more magnetoresistive sensing elements, which are comprised of amagnetoresistive material (e.g., nickel-iron (NiFe)), where theelectrical resistance of the magnetoresistive material may depend on astrength and/or a direction of the magnetic field present at themagnetoresistive material. Here, a sensing element may operate based onan anisotropic magnetoresistance (AMR) effect, a giant magnetoresistance(GMR) effect, a tunnel magnetoresistance (TMR) effect, or the like. Asanother example, a magnetic sensor may include one or more Hall-basedsensing elements that operate based on a Hall-effect. A magnetic anglesensor may include multiple sensing elements of one or more types.

As an additional example, resolver coils may be used as magneticsensors. However, it should be understood that the induced voltages ofthe resolver coils have to be demodulated before they can be used as xand y components for the calculation of the angle and the vector length.

A magnetic field component may be, for example, an x-magnetic fieldcomponent (Bx), a y-magnetic field component (By), or a z-magnetic fieldcomponent (Bz), where the Bx and By field components are in-plane to thechip, and Bz is out-of-plane to the chip in the examples provided. Asensing element may be sensitive to one component of the magnetic fieldaccording to its “sensitivity-axis” or “sensing axis”.

For example, measurement values (e.g., voltage) output by a sensingelement changes according to the magnetic field strength in thedirection of its sensing axis. For example, a sensing element that hasits sensitivity-axis aligned with an x-axis is sensitive to x-magneticfield component (Bx), whereas a sensing element that has itssensitivity-axis aligned with a y-axis is sensitive to y-magnetic fieldcomponent (By). Thus, two sensing elements may be configured to havetheir sensitivity-axes arranged orthogonal to each other.

According to one or more embodiments, a plurality of magnetic fieldangle sensors and a sensor circuitry may be both accommodated (i.e.,integrated) in the same chip. The sensor circuit may be referred to as asignal processing circuit and/or a signal conditioning circuit thatreceives one or more signals (i.e., sensor signals) from one or moremagnetic field sensing elements in the form of raw measurement data andderives, from the sensor signal, a measurement signal that representsthe magnetic field.

In some cases, a measurement signal may be differential measurementsignal that is derived from sensor signals generated by two sensingelements having a same sensing axis (e.g., two sensing elementssensitive to the same magnetic field component) using differentialcalculus. A differential measurement signal provides robustness tohomogenous external stray magnetic fields.

Signal conditioning, as used herein, refers to manipulating an analogsignal in such a way that the signal meets the requirements of a nextstage for further processing. Signal conditioning may include convertingfrom analog to digital (e.g., via an analog-to-digital converter),amplification, filtering, converting, biasing, range matching, isolationand any other processes required to make a sensor output suitable forprocessing after conditioning.

Thus, the sensor circuit may include an analog-to-digital converter(ADC) that converts the analog signal from the one or more sensingelements to a digital signal. The sensor circuit may also include adigital signal processor (DSP) that performs some processing on thedigital signal, to be discussed below. Therefore, a chip, which may alsobe referred to as an integrated circuit (IC), may include a circuit thatconditions and amplifies the small signal of one or more magnetic fieldsensing elements via signal processing and/or conditioning. It will alsobe appreciated that the described embodiments may be divided onto two ormore chips. In addition, the sensor circuit may include an optionaldemodulator that demodulates the x and y components for the case thatthe measurement is done with an alternating magnetic field as it is donein a resolver. The demodulation can be done in the analog domain, beforethe ADC, or in the digital domain via a DSP, after the A/D conversion.

A sensor device, as used herein, may refer to a device which includes asensor and sensor circuit as described above.

FIG. 1 is a block diagram illustrating a magnetic angle sensor 100according to one or more embodiments. The magnetic angle sensor 100 mayinclude two sensing elements Sx and Sy that are arranged to provideoutput signals corresponding to two orthogonal components of a magneticfield, such as an x-component of the magnetic field and a y-component ofthe magnetic field. In this case, the sensing element Sx is configuredto sense a sine angle component (e.g., x-component) of the magneticfield and the sensing element Sy is configured to sense a cosine anglecomponent (e.g., y-component) of the magnetic field. Thus, the twosensing elements Sx and Sy are configured to generate two sensor signals(e.g., a voltage signal Vx and a voltage signal Vy) that are phaseshifted from each other by 90°.

The magnetic angle sensor 100 also includes a sensor circuit 10 thatreceives the sensor signals from the sensing elements Sx and Sy forprocessing and for generation of an angle output signal corresponding toan orientation of the magnetic field. The sensor circuit 10 includes twosignal paths: an X signal path and a Y signal path. The signal-X on theX signal path may be in a form of a sinusoidal (sine) waveform thatrepresents an angular orientation of the target object, and the signal-Yon the Y signal path may be a similar waveform that is shifted 90° fromsignal-X. That is, signal-Y is a sinusoidal (cosine) waveform thatrepresents an angular orientation of the target object. It will beappreciated that while the examples herein describe the sine waveform asbeing used as signal-X and the cosine waveform as being used assignal-Y, the opposite may also be true so long as the two signals arephase shifted 90° from each other.

Signal paths X and Y may include an ADC 1 x and an ADC 1 y,respectively, that convert the sensor signal Vx and Vy of the respectivesignal path into a digital signal for further processing by a remainingportion of the sensor circuit 10.

A DSP may include a digital signal processing device or a collection ofdigital signal processing devices. The DSP may receive digital signalsfrom the ADCs 1 x and 1 y and may process the digital signals to formoutput signals destined for an external device, such as a controller(not illustrated). Each “block” may include one or more processors forprocessing one or more signals.

The DSP may include a temperature compensation (TC), self-calibration,and filter block 2, a signal conversion algorithm block 3, an optionalmemory element 4, and an angle protocol block 5.

The temperature compensation (TC), self-calibration, and filter block 2may receive the sensor signals Vx and Vy and a temperature sensor signalT, and perform one or more signal conditioning operations thereon beforeoutputting the compensated sensor signals Vx and Vy to the signalconversion algorithm block 3. The temperature compensation (TC),self-calibration, and filter block 2 may be considered optional in someapplications.

The signal conversion algorithm block 3 is configured to receive thecompensated sensor signals Vx and Vy for further processing. Forexample, the signal conversion algorithm block 3 may include one or moreprocessors and/or logic units that performs various signal conditioningfunctions, such as absolute signal conversion, normalization,linearization, self-testing, and so forth. One or more signalconditioning functions may be performed in combination with a lookuptable stored in the memory element 4. In other words, the signalconversion algorithm block 3 receives the sensor signals Vx and Vy fromthe sensing elements Sx and Sy, and converts the sensor signals intomeasurement signals (i.e., measurement values) Vx′ and Vy′ that is to beused for further calculations, such as angle calculations and vectorlength calculations.

Optional memory element 4 may include a read only memory (ROM) (e.g., anEEPROM), a random access memory (RAM), and/or another type of dynamic orstatic storage device (e.g., a flash memory, a magnetic memory, anoptical memory, etc.) that stores information and/or instructions foruse by the signal conversion algorithm block 3. In some implementations,optional memory element 4 may store information associated withprocessing performed by the signal conversion algorithm block 3.Additionally, or alternatively, optional memory element 4 may storeconfigurational values or parameters for the set of sensing elements Sxand Sy and/or information for one or more other elements of the anglesensor 100, such as ADCs 1 x and 1 y.

Thus, the temperature compensation (TC), self-calibration, and filterblock 2 and the signal conversion algorithm block 3, convert the sensorsignals Vx and Vy into measurement signals Vx′ and Vy′. The output ofthe signal conversion algorithm block 3 Vx′ and Vy′ is provided to anangle protocol block 5 that is configured to generate an angle signal asan output signal based on measurement signals Vx′ and Vy′. The angleprotocol block 5 may be a processor that is configured to apply an anglealgorithm (e.g., α=arctan(Vy/Vx)) for determining the angle of arotating magnetic field, and generate the angle signal that representsan angular value.

Ultimately, the angle protocol block 5 is configured to receive thesensor signals Vx and Vy or measurement signals derived therefrom (e.g.,compensated voltage signal Vx′ and compensated voltage signal Vy′). Theangle protocol block 5 is configured to calculate an angle of rotation(a) of a magnet that generates the magnetic field (and an angle ofrotation of a rotatable object to which the magnet is connected) basedon the sensor signals or measurement signals corresponding to the twoorthogonal components (e.g., α=arctan(Vy/Vx)).

In some cases, a functional safety check may be implemented in the anglesensor 100. For example, a vector length associated with the sensorsignals (e.g., a vector length (VL) equal to Vx²+Vy²) may be monitoredduring operation of the angle sensor as a functional safety check. Inone example, if the vector length remains substantially constant duringoperation of the angle sensor (e.g., after calibration and/ortemperature compensation), then safe operation of the angle sensor maybe assumed. However, such a functional safety check (e.g., based on twooutput signals) has limited accuracy and/or may have insufficientdiagnostic coverage due to being dependent on absolute values of theoutput signals.

In addition, besides the monitoring of the absolute vector length, theinvention monitors the change of the vector length. This has theadvantage that there is only a very narrow range between vector lengthvalues must be tolerated, since ambient influences like temperature ormechanical stress changes very slow.

FIG. 2A is a schematic block diagram of a magnetic angle sensor device200 according to one or more embodiments. The magnetic angle sensordevice 200 is a system that may be integrated on one or more chips. Themagnetic angle sensor device 200 includes several signal processingcircuits and blocks configured to process sensor signals and measurementsignals that, as a whole, make up a sensor circuit. It will beappreciated that the signal processing circuits and blocks may becombined into a single processor, microprocessor, DSP, and the like.Alternatively, the signal processing circuits and blocks may be providedin two or more processors, microprocessors, DSPs, and the like. The oneor more signal processing circuits and blocks can be integrated on asensor chip along with the sensing elements or be provided in amicrocontroller on system level.

FIG. 2B is a graph illustrating a vector length tolerance regionaccording to one or more embodiments. In particular, a vector length isplotted according to the equation VL=Vx²+Vy². The graph illustrates avector length plotted in x-y coordinates (i.e., based on the two sensedx and y magnetic field components), where +/−Ymax represent extrema of ay ADC conversion range and +/−Xmax represent extrema of an x ADCconversion range. Ideally, the length vector should track a circle, butsome degree of tolerance is used to account for non-idealities.

The graph illustrates a wide vector length tolerance region 11 and anarrow vector length tolerance region 12. The graph further illustratesa normal length vector 13 with a changing angle and a faulty vector 14,which is “stuck” at an x-value. Since x and y components are constantlychanging with a rotating magnetic field, the faulty length vector 14stuck at an x-value indicates that the sensed x-component is no longerchanging. This may be an indication that the sensing element Sx isfaulty.

The graph demonstrates that the changing normal length vector 13remained within the narrow vector length tolerance region 12, indicatingnormal operation. In contrast, the faulty length vector 14 goes outsidethe bounds of the narrow vector length tolerance region 12, indicatingfaulty behavior.

Turning back to FIG. 2A, the magnetic angle sensor device 200 includes afirst sensing element (Sx) 21 and a second sensing element (Sx) 22 thatgenerate sensor signals Vx and Vy, as described above.

The magnetic angle sensor device 200 also includes a first measurementcircuit 23 and a second measurement circuit 24 that generate measurementsignals Vx′ and Vy′, respectively, as described above.

The measurement circuits 23 and 24 may each include an ADC (e.g., ADC 1x or ADC 1 y) a temperature compensation (TC), self-calibration, andfilter block 2, a signal conversion algorithm block 3, and a memoryelement 4. Thus, the measurement circuits 23 and 24 each includes one ormore processors and/or logic units that performs various signalconditioning functions in order to derive the measurement values Vx′ andVy′ from the sensor signals Vx and Vy for use in further calculations.The measurement circuits 23 and 24 may be a microprocessor, such as aDSP, or a portion thereof.

The magnetic angle sensor device 200 further includes an angle protocolblock 25 configured to process the measurement values Vx′ and Vy′ togenerate an angle signal θ as an output angle according to an anglealgorithm (e.g., α=arctan(Vy′/Vx′). The angle protocol block 25 may beconfigured to generate and output an angle measurement at differentsample times.

The magnetic angle sensor device 200 further includes a vector lengthprotocol block 26 configured to process the measurement values Vx′ andVy′ to generate a vector length signal as an output vector lengthaccording to a vector length algorithm (e.g., VL=Vx′²+Vy′²). The vectorlength protocol block 26 is configured to generate and output a vectorlength measurement VL at different sample times, which may coincide withthe different sample times of the angle measurements. Thus, each vectorlength measurement VL may also correspond to an angle measurement.

The magnetic angle sensor device 200 further includes a vector lengthdifferentiation block 27 configured to calculate a vector lengthdifference between at least two vector length (VL) samples.

In one implementation, the vector length differentiation block 27 isconfigured to receive two adjacent VL samples (i.e., two samples takenat two consecutive sample times), and calculate a differencetherebetween to generate a differential vector length (e.g.,ΔVL=VL1−VL2).

Since the sampling rate of the angle measurements is high, the vectorlength check may not rely on only one measurement of the vector lengthchange. Thus, other implementations that use more than two adjacentsamples is also possible, which may vary in implementation based on theset of measured vector length changes criteria.

For example, in another implementation, the vector lengthdifferentiation block 27 is configured to receive two or more adjacentVL samples (i.e., two or more samples taken at consecutive sampletimes), calculate a differential vector length (ΔVL) between each pairof adjacent VL samples to generate a set of differential vector lengthvalues, and further calculate an average of the differential vectorlengths (ΔVL_(avg1)) at its output.

In another implementation, the vector length differentiation block 27 isconfigured to receive two or more adjacent VL samples (i.e., two or moresamples taken at consecutive sample times), calculate a differentialvector length (ΔVL) between each pair of adjacent VL samples to generatea set of differential vector length values, determine a differentialvector length minimum value (ΔVLmin) among the set of differentialvector length values, determine a differential vector length maximumvalue (ΔVLmax) among the set of differential vector length values, andoutput the minimum value (ΔVLmin) and the maximum value (ΔVLmax) at itsoutput as differential vector lengths to be evaluated.

In another implementation, the vector length differentiation block 27 isconfigured to receive two or more adjacent VL samples (i.e., two or moresamples taken at consecutive sample times), capture minimum and maximumvalues among the vector length samples, and calculate ΔVLmm=VLmax−VLminas the differential vector length.

In another implementation, the vector length differentiation block 27 isconfigured to receive two or more adjacent VL samples (i.e., two or moresamples taken at consecutive sample times), calculate a standarddeviation (stdev) of the adjacent VL samples as the differential vectorlength ΔVL_(SD) to be evaluated.

The magnetic angle sensor device 200 further includes a vector lengthvariance analysis block 28 configured to receive the outputs from thevector length differentiation block 27 (e.g., ΔVL, ΔVL_(avg1), ΔVLmin,ΔVLmax, ΔVLmm, and/or ΔVL_(SD)) and perform a variance analysis check onthe received information based on one or more predetermined tolerancethresholds. If a differential value exceeds predetermined tolerancethreshold, the vector length variance analysis block 28 may generate awarning signal indicative of a fault in the angle sensor device 200 andoutput the warning signal to an external device, such as an externalcontroller.

For example, vector length variance analysis block 28 may receive thedifferential vector length (ΔVL), and compare the differential vectorlength (ΔVL) to a minimum tolerance threshold value and a maximumtolerance threshold value. One or both of the minimum tolerancethreshold value and the maximum tolerance threshold value may define atolerance range or window in which the differential vector lengths areacceptable and indicate normal functionality.

Thus, if the differential vector length (ΔVL) is less than the minimumtolerance threshold value or greater than the maximum tolerancethreshold value, the vector length variance analysis block 28 determinesthat the differential vector length (ΔVL) is outside of the boundariesof the tolerance range and that a fault may exists within the magneticangle sensor device 200.

On the other hand, if the if the differential vector length (ΔVL) isequal to or greater than the minimum tolerance threshold value and equalto or less than the maximum tolerance threshold value, the vector lengthvariance analysis block 28 determines that the differential vectorlength (ΔVL) is within the boundaries of the tolerance range and thatthe magnetic angle sensor device 200 is operating within an acceptablemargin of error (i.e., the magnetic angle sensor device 200 is operatingnormally). If the differential vector length (ΔVL) is within theboundaries of the tolerance range, the vector length variance analysisblock 28 determines not to generate a warning signal.

The vector length variance analysis block 28 performs a similarevaluation for ΔVL_(avg1), ΔVLmm, ΔVLmin, ΔVLmax, and ΔVL_(SD), whereeach delta value output by the vector length differentiation block 27 isevaluated by a minimum tolerance threshold value and a maximum tolerancethreshold value. Different minimum and maximum tolerance thresholdvalues may be used depending on the type of delta variable is beingevaluated. The delta variables ΔVLmin and ΔVLmax may be evaluatedaccording to a same set of minimum and maximum tolerance thresholdvalues (i.e., via one tolerance range).

Alternatively, the vector length variance analysis block 28 maycalculate the absolute value (abs) of the differential vector lengths(ΔVL), determine one or more of the delta values based on the absolutevalue of the differential vector lengths (ΔVL), and monitor the deltavalue based on the maximum tolerance threshold value.

For example, the vector length variance analysis block 28 may use theabsolute value of a differential vector length (ΔVL), representing adifference between the first vector length and the second vector lengthas the vector length variance, and compare the vector length variance tothe maximum tolerance threshold value. If the absolute value of adifferential vector length (ΔVL) exceeds the maximum tolerance thresholdvalue, the vector length differentiation block 27 generates a warningsignal.

Alternatively, the vector length variance analysis block 28 maycalculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths, calculate a plurality of absolutevalues, each being an absolute value of one of the plurality ofdifferential vector lengths, and calculate an average value of theplurality of absolute values as the vector length variance.

Alternatively, the vector length variance analysis block 28 maycalculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths, calculate a plurality of absolutevalues, each being an absolute value of one of the plurality ofdifferential vector lengths, and determine at least one of a minimumabsolute value having a smallest value among the plurality of absolutevalues or a maximum absolute value having a largest value among theplurality of absolute values as the vector length variance.

Here, the vector length variance analysis block 28 may determine theminimum absolute value of the plurality of absolute values as a firstvector length variance, determine the maximum absolute value of theplurality of absolute values as a second vector length variance, comparethe minimum absolute value to the tolerance range, compare the maximumabsolute value to the tolerance range, and generate the warning signalon a condition that at least one of the first vector length variance orthe second vector length variance is outside the tolerance range. Here,when the maximum absolute value is outside of the tolerance range, itmeans that one of the delta samples was too large. On the other and,when the minimum absolute value is outside of the tolerance range, itmeans that all delta samples were too large.

The vector length differentiation block 27 may be configured to changethe type of delta variable it calculates and outputs to the vectorlength variance analysis block 28. As a result, the vector lengthvariance analysis block 28 may include a memory element that stores alook-up table that includes different sets of minimum and maximumtolerance threshold values (i.e., different sets of tolerance ranges)mapped to different types of delta variables, and may be configured toselect a set of minimum and maximum tolerance threshold values from thelook-up table based on the type of delta variable received.

In addition, the vector length variance analysis block 28 may monitorthe absolute vector length based on the vector length measurements VL inaddition to monitoring the change of the vector length. To do so, thevector length protocol block 26 and the vector length variance analysisblock 28 may be coupled together such that the vector length protocolblock 26 provides the vector length signal comprising vector lengthmeasurements VL to the vector length variance analysis block 28.

FIG. 3 is a schematic block diagram of a magnetic angle sensor device300 according to one or more embodiments. The magnetic angle sensordevice 300 is a system that may be integrated on one or more chips. Themagnetic angle sensor device 300 includes several signal processingcircuits and blocks configured to process sensor signals and measurementsignals that, as a whole, make up a sensor circuit. It will beappreciated that the signal processing circuits and blocks may becombined into a single processor, microprocessor, DSP, and the like.Alternatively, the signal processing circuits and blocks may be providedin two or more processors, microprocessors, DSPs, and the like.

The magnetic angle sensor device 300 is similar to magnetic angle sensordevice 200, with the exception that the magnetic angle sensor device 300includes a vector length processing block 37 instead of vector lengthdifferentiation block 27. The vector length processing block 37 mayinclude a high pass filter (HPF), a band pass filter (BPF), a low passfilter (LPF), or a time/frequency transform (i.e., a fast Fouriertransform (FFT)). Thus, in the alternative to a differentiation as usedin FIG. 2, the criterion for detecting faults in the vector length canalso be defined on (1) a high pass/band pass/low pass filtering or (2) aspectral analysis of the vector length samples, where the non-DCspectral components that depend on the vector length variance aremonitored. The HPF, BPF, and LPF may employ finite impulse response(FIR) filtering or infinite impulse response (IIR) filtering.

For example, two or more vector lengths (VL) may be received by thevector length processing block 37 in the form of a vector length signal,the frequency of which changes based on the variance between vectorlength samples. For example, the greater the variance, the greater theamplitude of the HPF output VLH. It is noted that the energy level ofnon-DC spectral components of the vector length signal also increases asthe variance between vector length samples increases, or decreases asthe variance between vector length samples decreases. As a result, theHPF output VLH can be evaluated in the same way as the ΔVL values. Forexample, the vector length variance analysis block 28 may detect if theamplitude of the HPF output VLH exceeds a threshold either in a positiveor a negative direction (i.e., whether the amplitude of the HPF outputVLH is outside a tolerance range).

If the vector length processing block 37 includes a high pass filter,then the high frequency components of the vector length signal arepassed on to the vector length variance analysis block 28. This occurswhen the vector length variance is large enough to produce frequencycomponents that are greater than the cutoff frequency of the high passfilter. Thus, the high frequency signal VLH is output by the vectorlength processing block 37 to the vector length variance analysis block28 for analysis.

The cutoff frequency of the high pass filter may be set to acorresponding vector length variance, such that when a differentialvector length (ΔVL) is within a tolerance range, the vector lengthsignal is attenuated by the high pass filter. On the other hand, whenthe differential vector length (ΔVL) is outside a tolerance range, thevector length signal is passed through by the high pass filter. If thevector length variance analysis block 28 receives the high frequencysignal VLH, which is deterministic of the differential vector length(ΔVL) being outside the tolerance range, the vector length varianceanalysis block 28 determines that the variance of the vector lengthexceeds normal operating conditions and generates a warning signal. Ifthe vector length variance analysis block 28 does not receive the highfrequency signal VLH, no warning signal is generated.

In addition to the high frequency signal VLH, the vector length varianceanalysis block 28 also receives the vector length samples (VL) from thevector length protocol block 26, as described above.

If the vector length processing block 37 includes a band pass filter,then the band-passed frequency components of the vector length signalare passed on to the vector length variance analysis block 28. Thisoccurs when the vector length variance produces frequency componentsthat are within the band of the band pass filter. Thus, band-passedsignal is output by the vector length processing block 37 to the vectorlength variance analysis block 28 for analysis.

If the vector length processing block 37 includes a time/frequencytransform, the vector length processing block 37 converts the vectorlength signal (continuous-time signal), for example, via DiscreteFourier Transform (DFT), into the frequency domain representation of thevector length signal, and outputs the frequency domain representationVLF to the vector length variance analysis block 28 for furtheranalysis.

The greater the variance in vector length samples, the higher the FFTcoefficients of the non-DC spectral components will be. Thus, there willbe non-DC spectral components in the frequency domain representationthat have a high energy. Conversely, the lower the variance in vectorlength samples, the more likely there will be non-DC spectral componentsin the frequency domain representation that have a low energy. Thevector length variance analysis block 28 is configured to analyze theenergy levels of the non-DC spectral components and determine whetherany non-DC spectral components are outside a tolerance range. Forexample, the vector length variance analysis block 28 may be configuredto compare the energy levels of the non-DC spectral components tominimum and maximum energy levels that define a tolerance range, andgenerate a warning signal if one or more energy levels is determined tobe outside the tolerance range.

In particular, vector length processing block 37 converts the vectorlength signal from a time domain into a frequency domain via a DFTalgorithm to generate a frequency domain vector length signal comprisingthe at least one extracted spectral component. Usually, a relativelywide range of frequency components will be extracted. The vector lengthprocessing block 37 may calculate a sum or weighted sum of the magnitudeof the at least one extracted spectral component, compare the sum or theweighted sum to the tolerance range, and generate the warning signal ona condition that the sum or the weighted sum is outside the tolerancerange.

In addition to the frequency domain representation VLF, the vectorlength variance analysis block 28 also receives the vector lengthsamples (VL) from the vector length protocol block 26, as describedabove.

FIG. 4 is a schematic block diagram of a magnetic angle sensor device400 according to one or more embodiments. The magnetic angle sensordevice 300 is a system that may be integrated on one or more chips. Themagnetic angle sensor device 400 includes several signal processingcircuits and blocks configured to process sensor signals and measurementsignals that, as a whole, make up a sensor circuit. It will beappreciated that the signal processing circuits and blocks may becombined into a single processor, microprocessor, DSP, and the like.Alternatively, the signal processing circuits and blocks may be providedin two or more processors, microprocessors, DSPs, and the like.

The magnetic angle sensor device 400 is similar to the magnetic anglesensor devices 200 and 300 in that it includes sensing elements 21 and22, measurement circuits 23 and 24, angle protocol block 25, and avector length protocol block 26. The magnetic angle sensor device 400further includes a vector length change processing block 47, which canbe either the vector length differentiation block 27 or the vectorlength processing block 37. The magnetic angle sensor device 400 furtherincludes the vector length variance analysis block 28, which may beconfigured to perform as described in reference to FIG. 2 or to FIG. 3.

The magnetic angle sensor device 400 further includes a temperaturesensor (ST) 41 and a temperature measurement circuit 42. The temperaturesensor 41 is configured to measure an ambient temperature and generate asensor signal V_(T) representative of the measured temperature. Thetemperature measurement circuit 42 is configured to perform signalprocessing and conditioning on the sensor signal V_(T), for example, ina similar manner as described in reference to measurement circuits 23and 24, and generate a temperature measurement signal V_(T)′.

The temperature measurement circuit 42 may also be configured tocalculate a temperature variance between two or more consecutivetemperature measurement samples.

The magnetic angle sensor device 400 further includes a stress sensor(Sσ) 43 and a stress measurement circuit 44. The stress sensor 43 isconfigured to measure a mechanical stress acting on the sensor chip andgenerate a sensor signal Vσ representative of the measured stress. Forexample, the stress sensor 43 may be a piezoresistive sensor integratedin a substrate of the sensor chip.

The stress measurement circuit 44 is configured to perform signalprocessing and conditioning on the sensor signal Vo, for example, in asimilar manner as described in reference to measurement circuits 23 and24, and generate a stress measurement signal Vσ′.

The stress measurement circuit 44 may also be configured to calculate astress variance between two or more consecutive stress measurementsamples.

For the temperature and the die stress measurements, the sampling ratesFS_T and FS_stress, respectively, can be lower than the sampling ratefor the angle FS_angle, since temperature and stress are slow changingproperties. Thus, FS_T<=FS_angle and FS_stress<=FS_angle.

The angle protocol block 25 may also be configured to calculate an anglevariance between two or more consecutive angle measurement samples. Theangle sampling rate or frequency may be equal to or greater than thesampling rate or frequency of the vector length calculation performed bythe vector length protocol block 26. In other words, the sampling rateof the vector length FS_VL implemented by the vector length protocolblock 26 is typically equal to the sampling rate of the anglemeasurement FS_angle implemented by the angle protocol block 25, but maybe less than the sampling rate FS_angle if, for example, computing poweris limited (i.e., FS_VL<=FS_angle). If the sampling frequency for theangle measurements is greater than the sampling frequency for the vectorlength calculation, a transfer function may be used that approximatesthe vector length variance function over the same time window based onthe lower number of available samples.

If the variance method is a standard deviation stdev, the vector lengthprocessing block 27 will use the average of a group of samples (N) thatare taken into account for the standard deviation and consequently thesampling rate of the standard deviation will be FS_stdev=FS_VL/N, whereN is an integer greater than 1.

If differences between consecutive vector lengths are used, eachvariance sample delivers a difference to the previous one. In this case,the sampling rate of the vector length difference FS_VLdiff will equalFS_VL.

In case variance measurements that employ filters, as in FIG. 3,realization can be found with or without decimations (D). Thus, thesampling rate of the variance measurements FS_variance_Filter=FS_VL orFS_variance_Filter=FS_VL/D, where the sampling is performed by thelength variance analysis block 28. In general, it can be said that thesampling rate of the vector length variance FS_variance<=FS_VL.

Analogous to the variance for the VL, the variance for stress andtemperature can be FS_variance_T<=FS_T or FS_variance_stress<=FS_stress.If the sampling rate for a temperature or a stress or their respectivevariances is lower than the sampling rate for the VL variance, it mightbe interpolated or in this case better said extrapolated to the samplingtime of the actual VL_variance sample. In other words, if the samplingrate for a temperature or a stress or their respective variances islower than the sampling rate for the VL variance, a transfer functionmay be used that approximates the vector length variance function overthe same time window based on the lower number of available samples.

The magnetic angle sensor device 400 further includes min/max thresholddetermination block 46 that is configured to select or extract a minimumtolerance threshold from a plurality of different minimum tolerancethresholds and select or extract a maximum tolerance threshold from aplurality of different maximum tolerance thresholds.

In particular, the min/max threshold determination block 46 may beconfigured to receive the temperature measurement signal V_(T)′ or atemperature variance measurement and select the minimum tolerancethreshold and the maximum tolerance threshold based on the measuredtemperature value or the temperature variance measurement value. Theselected minimum tolerance threshold and the maximum tolerance thresholdmay be extracted from a look-up table that stores minimum tolerancethresholds and the maximum tolerance thresholds mapped to differenttemperature values, different temperature variances, or differenttemperature ranges.

Alternatively, the VL thresholds may also be updated by the min/maxthreshold determination block 46 by being scaled with a linear functiondepending on the variance of the other measurements (temperature,stress, and/or angle). For example, updated threshold=currentthreshold*(1+scaleT*delta T+scale stress*delta stress+scale angel*deltaangel), where the current threshold may be an initial threshold or apreviously updated threshold. Additionally, scaleT represents a scalerfactor for temperature, scale stress represents a scaler factor forstress, scale angle represents a scaler factor for angle, delta Trepresents a measured variance in temperature, delta stress represents ameasured variance in stress, and delta angle represents a measuredvariance in angle.

The minimum tolerance threshold and the maximum tolerance threshold maybe analyzed and adjusted after each acquired angle sample or anglevariance measurement. Thus, the min/max threshold determination block 46may be further configured to receive angle measurement samples or anglevariance samples from the output of the angle protocol block 25.

The tolerance range may be widened or narrowed if the temperature oranother environmental parameter changes over the time during which thevector length samples are observed. Here, the minimum tolerancethreshold and the maximum tolerance threshold are adjusted in oppositedirections to adjust the width of the tolerance range.

The tolerance range may be shifted up or down if the temperature oranother environmental parameter changes over the time during which thevector length samples are observed and the sensitivity to this parameteris systematic. Here, the minimum tolerance threshold and the maximumtolerance threshold are adjusted in the same direction to adjust theoffset of the tolerance range.

The min/max threshold determination block 46 may then transmit thresholdinformation TH, including the selected minimum tolerance threshold andthe selected maximum tolerance threshold, to the vector length varianceanalysis block 28. The vector length variance analysis block 28 isconfigured to set its minimum tolerance threshold and the selectedmaximum tolerance threshold (i.e., its tolerance range) according to thereceived threshold information TH, and may adjust these thresholdsperiodically upon receiving updated threshold information TH.

Additionally, or alternatively, the min/max threshold determinationblock 46 may be configured to receive the stress measurement signal Vσ′or a stress variance measurement and select the minimum tolerancethreshold and the maximum tolerance threshold based on the measuredstress value or the stress variance measurement value. The selectedminimum tolerance threshold and the maximum tolerance threshold may beextracted from a look-up table that stores minimum tolerance thresholdsand the maximum tolerance thresholds mapped to different stress values,different stress variances, or different stress ranges, or may beupdated by using a linear function (e.g., updated threshold=currentthreshold*(1+scaleT*delta T+scale stress*delta stress+scale angel*deltaangel)).

The min/max threshold determination block 46 may then transmit thresholdinformation TH, including the selected minimum tolerance threshold andthe selected maximum tolerance threshold, to the vector length varianceanalysis block 28. The vector length variance analysis block 28 isconfigured to set its minimum tolerance threshold and the selectedmaximum tolerance threshold (i.e., its tolerance range) according to thereceived threshold information TH, and may adjust these thresholdsperiodically upon receiving updated threshold information TH.

The minimum tolerance threshold and the maximum tolerance threshold maybe analyzed and adjusted after each acquired angle sample or anglevariance measurement. Thus, the min/max threshold determination block 46may be further configured to receive angle measurement samples or anglevariance samples from the output of the angle protocol block 25.

The tolerance range may be widened or narrowed if the temperature oranother environmental parameter changes over the time during which thevector length samples are observed. Here, the minimum tolerancethreshold and the maximum tolerance threshold are adjusted in oppositedirections to adjust the width of the tolerance range.

The tolerance range may be shifted up or down if the temperature oranother environmental parameter changes over the time during which thevector length samples are observed and the sensitivity to this parameteris systematic. Here, the minimum tolerance threshold and the maximumtolerance threshold are adjusted in the same direction to adjust theoffset of the tolerance range.

Additionally, or alternatively, the min/max threshold determinationblock 46 may be configured to receive the angle measurement samples orangle variance measurement samples from the output of the angle protocolblock 25 for determining the minimum tolerance threshold and the maximumtolerance threshold. That is, the trajectory of the rotation vector maynot necessarily be an ideal circle due to shorter periodicity effectsintroduced by, for example, an AMR effect in GMR or TMR devices,exchange coupling between reference and free layer, form anisotropy,crystal anisotropy, etc. As a result, the minimum tolerance thresholdand the maximum tolerance threshold may be dependent on the change ofthe measured angle to take into account the non-ideal circulartrajectory of the rotational angle dependence of the magnetic sensor(GMR, AMR, TMR, Hall). Thus, min/max threshold determination block 46may adjust the minimum tolerance threshold and the maximum tolerancethreshold based on the measured angle θ or the measured angle variancebetween two or more consecutive angle measurements.

Thus, the measured temperature, stress, and angle may be used separatelyor in any combination to update and adjust the minimum and the maximumtolerance thresholds used by the vector length variance analysis block28 as environmental and device influences change over time.

Table I provides a summary of variants of the VL variance analysis andtheir respective use cases. VL change processing corresponds to theprocessing implemented by the vector length differentiation block 27.Threshold comparison corresponds to the type of threshold comparisonanalysis implemented by the vector length variance analysis block 28.All other blocks may by implemented independent of the used VL changeprocessing and the used threshold comparison analysis. That is, thevector length differentiation block 27 and the vector length varianceanalysis block 28 may be adapted according to the desired use casewithout changing the rest of the system.

TABLE I VL change Threshold processing comparison Use case Differencemin and max Immediate detection if any sample deviates Difference andmin and max Reduced influence of noise and averaging outliers Remark:For implementation averaging is replaced by sum and scaled min and maxthresholds instead of division by no of samples Difference and min andmax Further reduced influence of noise LPF (FIR or IIR) and outliersdepending on LPF order Remark: (configurable by LPF corner Differenceand frequency) LPF is one kind of LPF or BPF HPF (FIR or IIR) min andmax Reduced influence of noise and outliers (configurable by HPF cornerfrequency) BPF (FIR or IIR) min and max Further reduced influence ofnoise and outliers depending on BPF order (configurable by both BPFcorner frequencies) Absolute of max Immediate detection if any sampledifference deviates Absolute of max Reduced influence of noise anddifference and outliers but better detection of averaging deviationsthat change direction Remark: For during observation (typically forimplementation angle dependent errors) averaging is replaced by sum andscaled max thresholds instead of division by no of samples Absolute ofmax Further reduced influence of noise difference and and outliersdepending on LPF order LPF (configurable by LPF corner frequency) butbetter detection of deviations that change direction during observation(typically for angle dependent errors) Standard max Reduced influence ofnoise and deviation (RMS outliers with increased weight on version ofextremes but better detection of absolute deviations that changedirection difference and during observation (typically for average)angle dependent errors) Remark: For implementation division and sqrttypically omitted by squared and scaled threshold LPF (FIR or IIR) maxReduced influence of noise and filtered squared outliers with increasedweight on differences as extremes but configurable by filter modifiedcorner frequency better detection of approximation of deviations thatchange direction stdev during observation (typically for angle dependenterrors) Abs FFT and max Reduced influence of noise and out but(weighted) sum of configurable by FFT length, sampling non-DC frequencyand weighting coefficient components Combinations of Different Maycombine fast detection of large any above threshold absolute differencesAnd LPF for each filtered absolute differences with check smallerthreshold for deviations which remain or develop over several samples

Additional embodiments are provided below:

1. A magnetic angle sensor system, comprising:

a first magnetic sensor configured to generate a first sensor signal inresponse to a first component of a magnetic field;

a second magnetic sensor configured to generate a second sensor signalin response to a second component of the magnetic field; and

at least one signal processor configured to:

generate an angle signal including an angular value corresponding to anorientation of the magnetic field based on the first sensor signal andthe second sensor signal,

generate a vector length signal comprising a plurality of vector lengthscorresponding to the first sensor signal and the second sensor signalbased on the first sensor signal and the second sensor signal, whereineach of the plurality of vector lengths is sampled at a different sampletime of a plurality of consecutive sample times,

determine a vector length variance between at least two consecutivelysampled vector lengths of the plurality of vector lengths,

compare the determined vector length variance to a tolerance rangedefined by at least one of a minimum tolerance threshold and a maximumtolerance threshold, and

generate a warning signal on a condition that the determined vectorlength variance is outside the tolerance range.

2. The magnetic angle sensor system of embodiment 1, wherein the firstcomponent and the second component of the magnetic field are orthogonalto each other such that the first sensor signal and the second sensorsignal are shifted 90° from each other.

3. The magnetic angle sensor system of embodiment 1, wherein the atleast one signal processor is configured to determine not to generatethe warning signal on a condition that the determined vector lengthvariance is within the tolerance range.

4. The magnetic angle sensor system of embodiment 1, wherein the atleast two consecutively sampled vector lengths include a first vectorlength and a second vector length, and the vector length variance is adifferential vector length representing a difference between the firstvector length and the second vector length.

5. The magnetic angle sensor system of embodiment 1, wherein the atleast two consecutively sampled vector lengths include a first vectorlength and a second vector length, and the vector length variance is anabsolute value of a differential vector length representing a differencebetween the first vector length and the second vector length.

6. The magnetic angle sensor system of embodiment 1, wherein theplurality of vector lengths includes a plurality of pairs ofconsecutively sampled vector lengths, wherein the at least one signalprocessor is configured to:

calculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths,

calculate a plurality of absolute values, each being an absolute valueof one of the plurality of differential vector lengths, and

calculate an average value of the plurality of absolute values as thevector length variance.

7. The magnetic angle sensor system of embodiment 1, wherein theplurality of vector lengths includes a plurality of pairs ofconsecutively sampled vector lengths, wherein the at least one signalprocessor is configured to:

calculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths, and

determine at least one of a minimum differential vector length having asmallest value among the plurality of differential vector lengths or amaximum differential vector length having a largest value among theplurality of differential vector lengths as the vector length variance.

8. The magnetic angle sensor system of embodiment 7, wherein the atleast one signal processor is configured to:

determine the minimum differential vector length of the plurality ofdifferential vector lengths as a first vector length variance,

determine the maximum differential vector length of the plurality ofdifferential vector lengths as a second vector length variance,

compare the first vector length variance to the tolerance range,

compare the second vector length variance to the tolerance range, and

generate the warning signal on a condition that at least one of thefirst vector length variance or the second vector length variance isoutside the tolerance range.

9. The magnetic angle sensor system of embodiment 1, wherein theplurality of vector lengths includes a plurality of pairs ofconsecutively sampled vector lengths, wherein the at least one signalprocessor is configured to:

calculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths,

calculate a plurality of absolute values, each being an absolute valueof one of the plurality of differential vector lengths, and

determine at least one of a minimum absolute value having a smallestvalue among the plurality of absolute values or a maximum absolute valuehaving a largest value among the plurality of absolute values as thevector length variance.

10. The magnetic angle sensor system of embodiment 9, wherein the atleast one signal processor is configured to:

determine the minimum absolute value of the plurality of absolute valuesas a first vector length variance,

determine the maximum absolute value of the plurality of absolute valuesas a second vector length variance,

compare the minimum absolute value to the tolerance range,

compare the maximum absolute value to the tolerance range, and

generate the warning signal on a condition that at least one of thefirst vector length variance or the second vector length variance isoutside the tolerance range.

11. The magnetic angle sensor system of embodiment 1, wherein the atleast one signal processor is configured to:

calculate a standard deviation of the plurality of vector lengths as thevector length variance.

12. The magnetic angle sensor system of embodiment 1, wherein the atleast one signal processor configured to receive a measured temperatureor a measured temperature variance and adjust the tolerance range basedon the measured temperature or the measured temperature variance.

13. The magnetic angle sensor system of embodiment 1, wherein the atleast one signal processor configured to receive a measured mechanicalstress or a measured mechanical stress variance and adjust the tolerancerange based on the measured mechanical stress or the measured mechanicalstress variance.

14. The magnetic angle sensor system of embodiment 1, wherein the atleast one signal processor configured to:

adjust the tolerance range based on the angular value or an angularvariance between at least two consecutive angular values.

15. The magnetic angle sensor system of embodiment 1, furthercomprising:

a temperature sensor configured to measure a temperature; and

a stress sensor configured to measure a mechanical stress,

wherein the at least one signal processor configured to:

receive the angle signal, and

adjust the tolerance range based on the measured temperature, themeasured mechanical stress, and the angular value.

16. The magnetic angle sensor system of embodiment 15, wherein the atleast one signal processor is configured to sample the angular value ata first sampling rate, sample the plurality of vector lengths at asecond sampling rate that is equal to or less than the first samplingrate, sample the measured temperature at a third sampling rate that isequal to or less than the first sampling rate, and sample the measuredstress at a fourth sampling rate that is equal to or less than the firstsampling rate.

17. A magnetic angle sensor system, comprising:

a first magnetic sensor configured to generate a first sensor signal inresponse to a first component of a magnetic field;

a second magnetic sensor configured to generate a second sensor signalin response to a second component of the magnetic field; and

at least one signal processor configured to:

generate an angle signal including an angular value corresponding to anorientation of the magnetic field based on the first sensor signal andthe second sensor signal,

generate a vector length signal comprising a plurality of vector lengthscorresponding to the first sensor signal and the second sensor signalbased on the first sensor signal and the second sensor signal, whereineach of the plurality of vector lengths is sampled at a different sampletime of a plurality of consecutive sample times,

extract at least one spectral component of the vector length signal, theat least one spectral component being indicative of a vector lengthvariance between at least two consecutively sampled vector lengths ofthe plurality of vector lengths, and

generate a warning signal on a condition that the at least one extractedspectral component is outside a tolerance range.

18. The magnetic angle sensor system of embodiment 17, wherein:

the at least one signal processor comprises a high pass filter or a bandpass filter configured to receive the vector length signal and generatea filter-passed vector length signal comprising the at least oneextracted spectral component.

19. The magnetic angle sensor system of embodiment 17, wherein the atleast one signal processor is configured to:

convert the vector length signal from a time domain into a frequencydomain to generate a frequency domain vector length signal comprisingthe at least one extracted spectral component,

calculate a sum or weighted sum of a magnitude of the at least oneextracted spectral component,

compare the sum or the weighted sum to the tolerance range, and

generate the warning signal on a condition that the sum or the weightedsum is outside the tolerance range.

20. The magnetic angle sensor system of embodiment 17, wherein the atleast one signal processor is configured to receive a measuredtemperature or a measured temperature variance and adjust the tolerancerange based on the measured temperature or the measured temperaturevariance.

21. The magnetic angle sensor system of embodiment 17, wherein the atleast one signal processor is configured to receive a measuredmechanical stress or a measured mechanical stress variance and adjustthe tolerance range based on the measured mechanical stress or themeasured mechanical stress variance.

22. The magnetic angle sensor system of embodiment 17, wherein the atleast one signal processor is configured to:

adjust the tolerance range based on the angular value or an angularvariance between at least two consecutive angular values.

23. The magnetic angle sensor system of embodiment 17, furthercomprising:

a temperature sensor configured to measure a temperature; and

a stress sensor configured to measure a mechanical stress,

wherein the at least one signal processor configured to:

receive the angle signal, and

adjust the tolerance range based on the measured temperature, themeasured mechanical stress, and the angular value.

24. A method of performing a vector length variance check, the methodcomprising:

generating a first sensor signal in response to a first component of amagnetic field;

generating a second sensor signal in response to a second component ofthe magnetic field;

generating an angle signal including an angular value corresponding toan orientation of the magnetic field based on the first sensor signaland the second sensor signal;

generating a vector length signal comprising a plurality of vectorlengths corresponding to the first sensor signal and the second sensorsignal based on the first sensor signal and the second sensor signal,wherein each of the plurality of vector lengths is sampled at adifferent sample time of a plurality of consecutive sample times;

determining a vector length variance between at least two consecutivelysampled vector lengths of the plurality of vector lengths;

comparing the determined vector length variance to a tolerance rangedefined by at least one of a minimum tolerance threshold and a maximumtolerance threshold; and

generating a warning signal on a condition that the determined vectorlength variance is outside the tolerance range.

25. The method of performing the vector length variance check ofembodiment 24, further comprising:

determining not to generate the warning signal on a condition that thedetermined vector length variance is within the tolerance range.

26. The method of performing the vector length variance check ofembodiment 24, wherein the at least two consecutively sampled vectorlengths include a first vector length and a second vector length, andthe vector length variance is a differential vector length representinga difference between the first vector length and the second vectorlength.

27. The method of performing the vector length variance check ofembodiment 24, wherein the plurality of vector lengths includes aplurality of pairs of consecutively sampled vector lengths, the methodfurther comprising:

calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths; and

calculating an average value of the plurality of differential vectorlengths as the vector length variance.

28. The method of performing the vector length variance check ofembodiment 24, wherein the at least two consecutively sampled vectorlengths include a first vector length and a second vector length, andthe vector length variance is an absolute value of a differential vectorlength representing a difference between the first vector length and thesecond vector length.

29. The method of performing the vector length variance check ofembodiment 24, wherein the plurality of vector lengths includes aplurality of pairs of consecutively sampled vector lengths, the methodfurther comprising:

calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths;

calculating a plurality of absolute values, each being an absolute valueof one of the plurality of differential vector lengths; and

calculating an average value of the plurality of absolute values as thevector length variance.

30. The method of performing the vector length variance check ofembodiment 24, wherein the plurality of vector lengths includes aplurality of pairs of consecutively sampled vector lengths, the methodfurther comprising:

calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths; and

determining at least one of a minimum differential vector length havinga smallest value among the plurality of differential vector lengths or amaximum differential vector length having a largest value among theplurality of differential vector lengths as the vector length variance.

31. The method of performing the vector length variance check ofembodiment 30, further comprising:

determining the minimum differential vector length of the plurality ofdifferential vector lengths as a first vector length variance;

determining the maximum differential vector length of the plurality ofdifferential vector lengths as a second vector length variance;

comparing the first vector length variance to the tolerance range;

comparing the second vector length variance to the tolerance range; and

generating the warning signal on a condition that at least one of thefirst vector length variance or the second vector length variance isoutside the tolerance range.

32. The method of performing the vector length variance check ofembodiment 24, wherein the plurality of vector lengths includes aplurality of pairs of consecutively sampled vector lengths, the methodfurther comprising:

calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths;

calculating a plurality of absolute values, each being an absolute valueof one of the plurality of differential vector lengths; and

determining at least one of a minimum absolute value having a smallestvalue among the plurality of absolute values or a maximum absolute valuehaving a largest value among the plurality of absolute values as thevector length variance.

33. The method of performing the vector length variance check ofembodiment 32, further comprising:

determining the minimum absolute value of the plurality of absolutevalues as a first vector length variance;

determining the maximum absolute value of the plurality of absolutevalues as a second vector length variance;

comparing the minimum absolute value to the tolerance range;

comparing the maximum absolute value to the tolerance range; and

generating the warning signal on a condition that at least one of thefirst vector length variance or the second vector length variance isoutside the tolerance range.

34. The method of performing the vector length variance check ofembodiment 24, further comprising:

calculating a standard deviation of the plurality of vector lengths asthe vector length variance.

35. The method of performing the vector length variance check ofembodiment 24, further comprising:

adjusting the tolerance range based on a measured temperature or ameasured temperature variance.

36. The method of performing the vector length variance check ofembodiment 24, further comprising:

adjusting the tolerance range based on a measured mechanical stress or ameasured mechanical stress variance.

37. The method of performing the vector length variance check ofembodiment 24, further comprising:

adjusting the tolerance range based on the angular value or an angularvariance between at least two consecutive angular values.

38. The method of performing the vector length variance check ofembodiment 24, further comprising:

adjusting the tolerance range based on a measured temperature, ameasured mechanical stress, and the angular value.

39. The method of performing the vector length variance check ofembodiment 38, further comprising:

sampling the measured temperature, the measured mechanical stress, andthe angular value at a first sampling rate, a second sampling rate, anda third sampling rate, respectively; and

sampling the plurality of vector lengths at a fourth sampling rate,

wherein the first, the second, and the fourth sampling rates are equalto or less than the third sampling rate.

40. A method of performing a vector length variance check, the methodcomprising:

generating a first sensor signal in response to a first component of amagnetic field;

generating a second sensor signal in response to a second component ofthe magnetic field;

generating an angle signal including an angular value corresponding toan orientation of the magnetic field based on the first sensor signaland the second sensor signal;

generating a vector length signal comprising a plurality of vectorlengths corresponding to the first sensor signal and the second sensorsignal based on the first sensor signal and the second sensor signal,wherein each of the plurality of vector lengths is sampled at adifferent sample time of a plurality of consecutive sample times;

extracting at least one spectral component of the vector length signal,the at least one spectral component being indicative of a vector lengthvariance between at least two consecutively sampled vector lengths ofthe plurality of vector lengths; and

generating a warning signal on a condition that the at least oneextracted spectral component is outside a tolerance range.

41. The method of performing the vector length variance check ofembodiment 40, further comprising:

providing the vector length signal to a high pass filter or a band passfilter to generate a filter-passed vector length signal comprising theat least one extracted spectral component.

42. The method of performing the vector length variance check ofembodiment 40, further comprising:

converting the vector length signal from a time domain into a frequencydomain to generate a frequency domain vector length signal comprisingthe at least one extracted spectral component;

calculating a sum or weighted sum of a magnitude of the at least oneextracted spectral component;

comparing the sum or the weighted sum to the tolerance range; and

generating the warning signal on a condition that the sum or theweighted sum is outside the tolerance range.

43. The method of performing the vector length variance check ofembodiment 40, further comprising:

adjusting the tolerance range based on a measured temperature or ameasured temperature variance.

44. The method of performing the vector length variance check ofembodiment 40, further comprising:

adjusting the tolerance range based on a measured mechanical stress or ameasured mechanical stress variance.

45. The method of performing the vector length variance check ofembodiment 40, further comprising:

adjusting the tolerance range based on the angular value or an angularvariance between at least two consecutive angular values.

46. The method of performing the vector length variance check ofembodiment 40, further comprising:

adjusting the tolerance range based on a measured temperature, ameasured mechanical stress, and the angular value.

47. The method of performing the vector length variance check ofembodiment 46, further comprising:

sampling the measured temperature, the measured mechanical stress, andthe angular value at a first sampling rate, a second sampling rate, anda third sampling rate, respectively; and

sampling the plurality of vector lengths at a fourth sampling rate,

wherein the first, the second, and the fourth sampling rates are equalto or less than the third sampling rate.

While various embodiments have been described, it will be apparent tothose of ordinary skill in the art that many more embodiments andimplementations are possible within the scope of the disclosure.Accordingly, the invention is not to be restricted except in light ofthe attached claims and their equivalents. With regard to the variousfunctions performed by the components or structures described above(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurethat performs the specified function of the described component (i.e.,that is functionally equivalent), even if not structurally equivalent tothe disclosed structure that performs the function in the exemplaryimplementations of the invention illustrated herein.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective acts of these methods.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware, or any combination thereof.For example, various aspects of the described techniques may beimplemented within one or more processors, including one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), or any other equivalent integrated ordiscrete logic circuitry, as well as any combinations of suchcomponents. The term “processor” or “processing circuitry” may generallyrefer to any of the foregoing logic circuitry, alone or in combinationwith other logic circuitry, or any other equivalent circuitry. A controlunit including hardware may also perform one or more of the techniquesof this disclosure. Such hardware, software, and firmware may beimplemented within the same device or within separate devices to supportthe various techniques described in this disclosure.

Although various exemplary embodiments have been disclosed, it will beapparent to those skilled in the art that various changes andmodifications can be made which will achieve some of the advantages ofthe concepts disclosed herein without departing from the spirit andscope of the invention. It will be obvious to those reasonably skilledin the art that other components performing the same functions may besuitably substituted. It is to be understood that other embodiments maybe utilized and structural or logical changes may be made withoutdeparting from the scope of the present invention. It should bementioned that features explained with reference to a specific figuremay be combined with features of other figures, even in those notexplicitly mentioned. Such modifications to the general inventiveconcept are intended to be covered by the appended claims and theirlegal equivalents.

What is claimed is:
 1. A magnetic angle sensor system, comprising: afirst magnetic sensor configured to generate a first sensor signal inresponse to a first component of a magnetic field; a second magneticsensor configured to generate a second sensor signal in response to asecond component of the magnetic field; and at least one signalprocessor configured to: generate an angle signal including an angularvalue corresponding to an orientation of the magnetic field based on thefirst sensor signal and the second sensor signal, generate a vectorlength signal comprising a plurality of vector lengths corresponding tothe first sensor signal and the second sensor signal based on the firstsensor signal and the second sensor signal, wherein each of theplurality of vector lengths is sampled at a different sample time of aplurality of consecutive sample times, determine a vector lengthvariance between at least two consecutively sampled vector lengths ofthe plurality of vector lengths, compare the determined vector lengthvariance to a tolerance range defined by at least one of a minimumtolerance threshold and a maximum tolerance threshold, and generate awarning signal on a condition that the determined vector length varianceis outside the tolerance range.
 2. The magnetic angle sensor system ofclaim 1, wherein the first component and the second component of themagnetic field are orthogonal to each other such that the first sensorsignal and the second sensor signal are shifted 90° from each other. 3.The magnetic angle sensor system of claim 1, wherein the at least onesignal processor is configured to determine not to generate the warningsignal on a condition that the determined vector length variance iswithin the tolerance range.
 4. The magnetic angle sensor system of claim1, wherein the at least two consecutively sampled vector lengths includea first vector length and a second vector length, and the vector lengthvariance is a differential vector length representing a differencebetween the first vector length and the second vector length.
 5. Themagnetic angle sensor system of claim 1, wherein the at least twoconsecutively sampled vector lengths include a first vector length and asecond vector length, and the vector length variance is an absolutevalue of a differential vector length representing a difference betweenthe first vector length and the second vector length.
 6. The magneticangle sensor system of claim 1, wherein the plurality of vector lengthsincludes a plurality of pairs of consecutively sampled vector lengths,wherein the at least one signal processor is configured to: calculate aplurality of differential vector lengths, each corresponding to adifferent one of the plurality of pairs of consecutively sampled vectorlengths and each representing a difference between a first vector lengthand a second vector length of its corresponding pair of consecutivelysampled vector lengths, calculate a plurality of absolute values, eachbeing an absolute value of one of the plurality of differential vectorlengths, and calculate an average value of the plurality of absolutevalues as the vector length variance.
 7. The magnetic angle sensorsystem of claim 1, wherein the plurality of vector lengths includes aplurality of pairs of consecutively sampled vector lengths, wherein theat least one signal processor is configured to: calculate a plurality ofdifferential vector lengths, each corresponding to a different one ofthe plurality of pairs of consecutively sampled vector lengths and eachrepresenting a difference between a first vector length and a secondvector length of its corresponding pair of consecutively sampled vectorlengths, and determine at least one of a minimum differential vectorlength having a smallest value among the plurality of differentialvector lengths or a maximum differential vector length having a largestvalue among the plurality of differential vector lengths as the vectorlength variance.
 8. The magnetic angle sensor system of claim 7, whereinthe at least one signal processor is configured to: determine theminimum differential vector length of the plurality of differentialvector lengths as a first vector length variance, determine the maximumdifferential vector length of the plurality of differential vectorlengths as a second vector length variance, compare the first vectorlength variance to the tolerance range, compare the second vector lengthvariance to the tolerance range, and generate the warning signal on acondition that at least one of the first vector length variance or thesecond vector length variance is outside the tolerance range.
 9. Themagnetic angle sensor system of claim 1, wherein the plurality of vectorlengths includes a plurality of pairs of consecutively sampled vectorlengths, wherein the at least one signal processor is configured to:calculate a plurality of differential vector lengths, each correspondingto a different one of the plurality of pairs of consecutively sampledvector lengths and each representing a difference between a first vectorlength and a second vector length of its corresponding pair ofconsecutively sampled vector lengths, calculate a plurality of absolutevalues, each being an absolute value of one of the plurality ofdifferential vector lengths, and determine at least one of a minimumabsolute value having a smallest value among the plurality of absolutevalues or a maximum absolute value having a largest value among theplurality of absolute values as the vector length variance.
 10. Themagnetic angle sensor system of claim 9, wherein the at least one signalprocessor is configured to: determine the minimum absolute value of theplurality of absolute values as a first vector length variance,determine the maximum absolute value of the plurality of absolute valuesas a second vector length variance, compare the minimum absolute valueto the tolerance range, compare the maximum absolute value to thetolerance range, and generate the warning signal on a condition that atleast one of the first vector length variance or the second vectorlength variance is outside the tolerance range.
 11. The magnetic anglesensor system of claim 1, wherein the at least one signal processor isconfigured to: calculate a standard deviation of the plurality of vectorlengths as the vector length variance.
 12. The magnetic angle sensorsystem of claim 1, wherein the at least one signal processor configuredto receive a measured temperature or a measured temperature variance andadjust the tolerance range based on the measured temperature or themeasured temperature variance.
 13. The magnetic angle sensor system ofclaim 1, wherein the at least one signal processor configured to receivea measured mechanical stress or a measured mechanical stress varianceand adjust the tolerance range based on the measured mechanical stressor the measured mechanical stress variance.
 14. The magnetic anglesensor system of claim 1, wherein the at least one signal processorconfigured to: adjust the tolerance range based on the angular value oran angular variance between at least two consecutive angular values. 15.A method of performing a vector length variance check, the methodcomprising: generating a first sensor signal in response to a firstcomponent of a magnetic field; generating a second sensor signal inresponse to a second component of the magnetic field; generating anangle signal including an angular value corresponding to an orientationof the magnetic field based on the first sensor signal and the secondsensor signal; generating a vector length signal comprising a pluralityof vector lengths corresponding to the first sensor signal and thesecond sensor signal based on the first sensor signal and the secondsensor signal, wherein each of the plurality of vector lengths issampled at a different sample time of a plurality of consecutive sampletimes; determining a vector length variance between at least twoconsecutively sampled vector lengths of the plurality of vector lengths;comparing the determined vector length variance to a tolerance rangedefined by at least one of a minimum tolerance threshold and a maximumtolerance threshold; and generating a warning signal on a condition thatthe determined vector length variance is outside the tolerance range.16. The method of performing the vector length variance check of claim15, further comprising: determining not to generate the warning signalon a condition that the determined vector length variance is within thetolerance range.
 17. The method of performing the vector length variancecheck of claim 15, wherein the at least two consecutively sampled vectorlengths include a first vector length and a second vector length, andthe vector length variance is a differential vector length representinga difference between the first vector length and the second vectorlength.
 18. The method of performing the vector length variance check ofclaim 15, wherein the plurality of vector lengths includes a pluralityof pairs of consecutively sampled vector lengths, the method furthercomprising: calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths; andcalculating an average value of the plurality of differential vectorlengths as the vector length variance.
 19. The method of performing thevector length variance check of claim 15, wherein the at least twoconsecutively sampled vector lengths include a first vector length and asecond vector length, and the vector length variance is an absolutevalue of a differential vector length representing a difference betweenthe first vector length and the second vector length.
 20. The method ofperforming the vector length variance check of claim 15, wherein theplurality of vector lengths includes a plurality of pairs ofconsecutively sampled vector lengths, the method further comprising:calculating a plurality of differential vector lengths, eachcorresponding to a different one of the plurality of pairs ofconsecutively sampled vector lengths and each representing a differencebetween a first vector length and a second vector length of itscorresponding pair of consecutively sampled vector lengths; calculatinga plurality of absolute values, each being an absolute value of one ofthe plurality of differential vector lengths; and calculating an averagevalue of the plurality of absolute values as the vector length variance.